Highlight text in PDF Files on a webpage

I'm new to a lot of things, and I'm trying to highlight text in a PDF file that will be rendered on my page. I came across TCPDF in my reading, but in the documentation, I was not able to see anything that can help me do that.

Basically, I want to do PDF reporting (see Turnitin). They highlight the plagiarized text in the PDF using different colors. Meaning I want to search for plagiarized strings in the pdf and highlight them. Currently, I'm using PDFParser to read all the text in the pdf to a string, highlight the plagiarized substrings and display entire string on html page. It's highlighted, but looks very very messy.

I have been stuck for a while. Is there any plugin that can help me do this?

Help is appreciated. Thanks.